1. Area of the Art
The present invention relates generally to closed container sampling systems, such as clinical chemistry analyzers, and, more specifically, to piercing stations for a closed container sampling system.
2. Description of the Prior Art
Clinical chemistry sampling and analyzing systems often use closed containers to contain samples to be analyzed. One of the initial and necessary functions of such sampling systems is to pierce the cap or stopper on closed containers in which the samples are contained to obtain an opening on the cap or stopper for the subsequent insertion of a sampling probe. This cap piercing function is often performed by a cap piercing station of the sampling system.
In conventional sampling systems, the cap piercing station often employs piercing blades that have an X-shaped cross-section. This type of conventional piercing blade with an X-shaped cross-section appears to be able to pierce through caps or stoppers that are relatively thin. However, there are several disadvantages of this conventional type of piercing blade with an X-shaped cross-section.
One of the major disadvantages of the conventional type of a piercing blade with an X-shaped cross-section is that it is not suitable for piercing thick (i.e., approximately xe2x85x9cxe2x80x3) caps or stoppers that are made of rubber material or the like. When inserting a sampling probe into the X-shaped cut made on the cap or stopper, the probe requires too much force to penetrate, resulting in motion errors and stalling the stepper motor drive. In addition, during withdrawal of the blades and the probe, the container tends to be lifted up together with the blades or probe and is hard to be held down.
Another disadvantage of this conventional type of a piercing blade with an X-shaped cross-section is that when a sample probe is subsequently inserted through the X-shaped cut left on the cap or stopper, the sample probe tends to re-seal the cap or stopper. This changes the pressure profile inside the sample container (depending on the amount of sample in the container) which can compromise the aspiration of the sample and the clot detection system that relies on detecting pressure variations during the aspiration cycle.
A further disadvantage of this conventional type of piercing blades with an X-shaped cross-section is that a false level sense may be produced when a probe is inserted into the container through a pierced cap or stopper. Oftentimes, container caps or stoppers are made with button shaped silicone rubber pieces supported by metallic foil closures. While piercing blades with an X-shaped cross-section can punch through the metallic foil, they only cut the metallic foil with an X-shaped cut. When the sampling probe later passes through the cap or stopper to reach the sample, it often touches the foil and thereby triggers a capacitance shift, which produces a false level sense that causes the system to believe that the sample fluid level is reached before the sample probe really reaches the fluid level.
Therefore, it is desirable to provide a piercing station with piercing blades of a new design that can reliably pierce thick caps or stoppers made of rubber or like materials and can also overcome the disadvantages of the conventional type of piercing blades with an X-shaped cross-section.
The present invention is directed to a piercing station for a closed container sampling system, such as a clinical chemistry analyzer.
It is one of the primary objects of the present invention to provide a piercing station for a closed container sampling system, such as a clinical chemistry analyzer. The piercing station utilizes newly designed and constructed piercing blades that can reliably pierce thick caps or stoppers made of rubber or like materials and can also overcome the disadvantages of the conventional type of piercing blades with an X-shaped cross-section.
The cap piercing station of the present invention utilizes piercing blades having an H-shaped cross-section, which cut an H-shaped opening in a cap or stopper on the top of a sample container. When a sampling probe is subsequently inserted, it stretches the opening into an eye-shaped opening, which provides the necessary ventilation for pressure equalization.
The cap piercing station of the present invention is further designed to work with handling racks that contain different sized containers and employs a cap presence sensor for detecting whether a cap or stopper is present at the top of a container for piercing. It also utilizes a shuttle mechanism for washing the blades between each piercing operation to eliminate carry-over contamination between sample containers. In addition, it incorporates a hydro-pneumatic lubrication and washing mechanism for lubricating and washing the blade between each piercing operation. The piercing station is also well-suited for use in an existing CTS system.
These and other objects and advantages are achieved in a piercing station that includes a structural frame having two vertical guide rods and a carriage assembly slidably mounted on guide rods. A step motor is provided to drive a lead screw, which in turn drives the carriage assembly to move up or down along the guide rod(s). A blade holder is mounted on the upper end of the carriage assembly. An alignment block assembly, which is independent of the carriage, slides along the guide rods, and is lifted and lowered by the vertical motion of the carriage assembly. The blade holder holds a piercing blade assembly, which includes a center blade with two parallel rows of three lengthwise slots, and two cross blades, which interlock with the center blade in its slots, respectively, such that the blade assembly has a generally modified H-shaped cross-section for piercing a thick cap or stopper on a sample container. The alignment block assembly is biased by a return spring for holding the container down when the blade assembly is being withdrawn after piercing the cap or stopper. Mounted on the alignment block assembly and cantilevered over the sample container is an alignment arm assembly. The arm assembly has a wash tower and a wick holder, in turn, mounted to it, so that they are centered above the sample container station. The design is such that the blade assembly must pass through the inside of the wick holder, wick assembly, wash station (or xe2x80x9cshowerxe2x80x9d), and through the cap or stopper of the sample container, if appropriate. Included on the arm assembly is a cap sensor, which determines whether or not there is a cap present, or if it is merely an open tube. The arm centers the tube (regardless of cap outer diameter) so that the subsequent cut is aligned with the tube center. Another sensor determines the point of vertical contact between the arm and the stopper and, thus, the height of the tube. A hydro-pneumatic system provides the metered lubrication and washing of the blades, after piercing a sample cap. Two fittings attach to the wick holder. The fitting supplying the wash function feeds wash solution or D.I. water into the wash station via a set of nozzles. The other fitting feeds a small amount of silicone oil into a wick, through which the blades pass on each cycle.
The major unique and novel features of the cap piercing station of the present invention include the design and construction of piercing blades with an H-shaped cross-section, the use of a cap presence sensor, the ability to handle various sized containers, and the design and construction of the automated washing and lubrication mechanism for washing and lubricating the blades between piercing operations to prevent contamination caused by carry-over of samples.
Such an arrangement has been found to provide a number of advantages. As explained in greater detail below, the new piercing blades with an H-shaped cross-section are well-suited for piercing thick caps or stoppers made of rubber or like materials. A sampling probe can be easily inserted into the H-shaped cut made on the cap or stopper, thereby reducing motion errors and avoiding stalling the stepper motor drive. The blades and probe can also be easily withdrawn without lifting up the sample containers. The eye-shaped opening made by the insertion of the probe also provides adequate ventilation to maintain a proper pressure profile inside the container. It also avoids the problem of metallic foil closure, thereby eliminating any false level sense when the probe is inserted into the container through the pierced cap or stopper.
The invention is defined in its fullest scope in the appended claims and is described below in its preferred embodiments.